PL249474B1 - Method of producing composite elements with hybrid structure, a head for their production and a composite element with hybrid structure - Google Patents

Abstract

The invention provides a method for manufacturing composite elements (1) or (1') with a hybrid structure, a head for their production, and a composite element with a hybrid structure, applicable to the production of components with the required high directional stiffness and mechanical strength at minimal weight. The essence of the invention is that in the first stage of the method, a structural core with a heterogeneous structure is printed using 3D printing technology, and then in the second stage, an outer layer is printed on the outer surface of the structural core using continuous fiber in a polymer matrix using 3D technology.

Description

Description of the invention

The invention is a method for manufacturing composite elements with a hybrid structure, a head for their production, and a composite element with a hybrid structure, applicable to the production of components with the required high directional stiffness and mechanical strength at minimal weight. Components containing composite elements with a hybrid structure are used in the aviation, space, and automotive industries, and are particularly suitable for the production of load-bearing frames, supports, and girders. The invention finds practical application in the production of specialized sports equipment, the components of which can deflect for shock absorption, and is particularly suitable for the production of bicycle frames, ski equipment, tennis rackets, and the like.

Previously, to obtain a composite element composed of high-strength fiber impregnated with a binder, it was necessary to create a mold for the element, place binder-impregnated fabric forms inside, and subject them to a curing process. A vacuum bag is used to achieve pressure, or for specific elements, the fabric forms can be placed on a core, for example, made of foamed plastic, which facilitates fabric alignment and can provide pressure when enclosed in the mold. After the binder has cured, the core is removed, for example, through chemical dissolution. A limitation of this technology is the time-consuming process and the high cost of mold making.

Continuous Fiber Fused Deposition Modeling (FDM) is another popular 3D printing technology, where a single filament bundle is infused with resin or molten thermoplastic and extruded through a print head. A limitation of this technology is that the filaments are laid down layer by layer only in the printing plane, i.e., horizontally. In practice, this method can only be used to produce components with high strength parameters in a single plane.

Another known method involves printing a thermoplastic core with layers arranged in a single plane in a single process (Fused Deposition Modeling, FDM). A layer of continuous fiber can then be placed on top of this core, allowing for directional fiber alignment on the core surface. The limitations of this technology are that it allows for only components with simplified shapes, and the core's structural complexity is limited, while its weight is significant.

The essence of the method for manufacturing composite elements with a hybrid structure, using the control of the printing head according to algorithms previously prepared for printing elements in 3D technology, is that in the first stage of the method, a structural core with a heterogeneous structure is printed using 3D printing technology, in accordance with the model and algorithm previously adapted for the production of a heterogeneous core structure, and then in the second stage of the method, on the outer surface of the structural core, the printing head prints an outer layer with a continuous fiber in a polymer matrix in 3D technology, the fibers of which are arranged directionally, in accordance with the model and algorithm previously adapted to control the movement of the printing head for the production of the outer layer.

Preferably, fibers made of an electroshrinkable material such as artificial muscle are incorporated into the surface of the structural core.

Preferably, the non-uniform structure of the structural core is modeled and printed according to an algorithm that takes into account the local mechanical properties of the structural core, optimized with respect to the directional arrangement of the fibers in the outer layer and relating to the strength properties of the outer layer.

The preferred directional arrangement of the fibers in the outer layer is determined at the stage of modeling the composite element, taking into account the non-uniform mechanical properties of the composite core.

Preferably, 3D printing of the structural core is performed using the powder method.

Preferably, the movement of the print head is controlled by one robot arm to which the print head is connected mechanically and electrically.

Preferably, the movement of the print head is controlled by two robot arms, to which it is alternately connected mechanically and electrically.

The essence of the head for manufacturing composite elements with a hybrid structure, located on an industrial robot arm designed for 3D printing of composite elements, which is equipped with a printing unit for continuous filament printing, is that the head according to the invention has at least two mechanical head connections that secure the head to one of the robot arms and at least two receiving elements of the energy transfer system. Each robot arm is equipped with a transmitting element of the energy transfer system and a mechanical arm connection that is compatible with each of the mechanical head connections, forming the head's mounting element.

Preferably, the element securing the head to the robot arm is a pneumatic gripper or a magnetic gripper.

Preferably, the receiving element of the energy transmission system and the transmitting element of the energy transmission system are contact systems or wireless systems.

Preferably, the head comprises a printing unit that is adapted to print only one type of fiber with specific mechanical properties, while for each other type of fiber a separate head or heads are used, which are used interchangeably.

The essence of a hybrid composite element, which takes the form of a three-dimensional component with a predetermined shape, is that it contains a structural core constituting the framework of the three-dimensional component, in the form of a heterogeneous three-dimensional structure manufactured using 3D printing technology, on which a permanently placed outer layer is made of directional fibers bound by a polymer matrix. The outer layer is manufactured using 3D printing technology using continuous fibers.

Preferably, the structural core contains additional fibers made of an electroshrinkable material such as artificial muscle, which are incorporated into the surface of the core.

Preferably, the structural core is made of a material adapted to create a permanent connection with the polymer matrix of the outer layer.

Preferably, the material from which the structural core is made is identical to the polymer matrix of the outer layer.

Preferably, the outer layer contains different types of fibers with different mechanical parameters located in a polymer matrix.

Preferably, the outer layer fibers are at least two types selected from glass, carbon, aramid, flax, basalt or hemp fibers.

The advantage of the method according to the invention is that it enables the production of composite elements with a hybrid structure with mechanical properties superior to composite elements made using molds. The absence of the need for expensive molds allows for significant savings in the production of these elements. Furthermore, the absence of molds significantly accelerates the production cycle.

Compared to known 3D printing technologies, the advantage of the method according to the invention is that it allows the production of components with complex shapes, e.g. any overhangs, closed shapes such as a torus and with any direction of fiber arrangement on the component surface.

The advantage of the head according to the invention is its design, which allows for a reduced weight and miniaturization, which in turn allows for the use of a robot with a smaller payload and reduced energy consumption in the process. This is possible because instead of using a single large head equipped with a complex system of dispensers for different fiber types, it is possible to use multiple heads attached to an industrial robot arm or arms, where individual heads can be equipped with different fiber types with different mechanical properties. The detachable connection of the head and the industrial robot arm or arms allows for the removal and reattachment of the robot arm head during the printing process, which additionally enables the production of components with more complex shapes or those containing closed sections, such as a torus or a bicycle frame triangle, which would be impossible to produce using a head permanently attached to the robot arm.

The advantage of the composite element with a hybrid structure according to the invention is that the directional fiber arrangement of the element's outer layer, combined with the heterogeneous distribution of the structural core structure, allows for increased strength, as the element's portions subjected to greater mechanical loads are characterized by a higher material density in the structural core structure. The presence of a structural core in the composite element means that the outer layer of the element, necessary to achieve the required mechanical strength, can be thinner than without such a core. Another advantage of a composite element with a hybrid structure is that through the appropriate fiber arrangement in the outer layer and the selection of the structural core structure's cross-linking, a component can be achieved that is highly flexible in precisely defined directions while maintaining high stiffness in other defined directions.

In the case of a composite element with a hybrid structure equipped with artificial muscle fibers controlled by electrical impulses, the resulting element bends in a predetermined, highly flexible direction. An example of such an element's application is an aircraft wing, which can be controlled by skeletal deflection of the airfoil instead of using movable flaps and ailerons. This simplifies the wing's structure, reduces its weight, and improves its aerodynamic efficiency.

The invention is presented in an exemplary embodiment in the drawing, in which Fig. 1 schematically shows the implementation of the method using a printing head attached to one of the arms of an industrial robot during printing of the outer layer of a composite element, with the second arm of the robot taking over the printing head from the first arm, marked with a dashed line, Fig. 2 schematically shows the structure of the printing head, Fig. 3 shows an exemplary composite element with a hybrid structure 1 in the first embodiment of the invention for a fragment of a bicycle frame, and Fig. 4 shows an exemplary composite element with a hybrid structure 1' in the second embodiment of the invention for a fragment of a bicycle frame.

The method of manufacturing a composite element with a hybrid structure 1 begins with the production of a structural core 1a using a 3D printing method, which is not shown in the drawing. Preferably, the core is obtained using powder printing technology: SLS (Selective Laser Sintering, Binder Jetting, etc.), which enables the printing of complex structures not limited by the need for supports. In the case of manufacturing a composite element with a hybrid structure 1', additional electroshrinkable fibers of the artificial muscle type 1c are incorporated into the surface of the core 1'a, which is carried out, for example, by placing them in recesses on the surface of the core 1'a, planned at the design stage and created during the process of printing the core 1'a. After manufacturing the structural core 1a or 1'a, the second stage of the method of manufacturing the composite element 1 or 1' with a hybrid structure is the formation of the outer layer 1b, which is shown in Fig. 1. The second stage is carried out by means of 3D printing with a continuous fiber (Continuous Fiber 3dp) saturated with a binder and using a printing head 2 connected to a robot arm 3, computer-controlled in such a way that the head 2 arranges the composite fibers on the surface of the structural core 1a or 1'a directionally in a manner consistent with the previously prepared control process and algorithm of this process.

If it is necessary to produce elements with more complex shapes or containing closed parts, such as a torus or a triangle of a bicycle frame, it is necessary for at least two robot arms 3 and 3a to be involved in the printing process and for the printing head 2 to be connected to them alternately.

Preferably, the material used to print the core is identical to the binder material of the outer layer 1b, produced in the second stage of the process, in order to ensure the best connection of the core 1a or 1'a and the outer layer 1b. Preferably, the structural material of the core 1a or 1'a and the binder of the outer layer 1b is a thermoplastic material which, in addition to favorable mechanical properties, is characterized by ease of recycling. For example, such a binder is polyamide (PA), ABS (Acrylonitrile butadiene styrene), PET (Polyethylene terephthalate), PLA (Polylactide).

A printing head 2 for manufacturing composite elements with a hybrid structure 1 or 1' is located on at least one arm 3, 3a of an industrial robot (fig. 1), which is designed to print composite elements using continuous filament 3D printing technology. The head 2 is equipped with at least two mounting elements in the form of mechanical head connections 4b, enabling its disconnection via a mechanical connection of arm 4a from one robot arm, for example 3, and its connection to the other arm 3a during the printing process. The mechanical connection of head 4b and the mechanical connection of arm 4a, when connected, form mounting elements 4, which enable both mechanical mounting of head 2 to the industrial robot arms as well as electrical power supply of head 2 and control of its operation. To ensure easy disconnection and connection of the head during the printing process, the mechanical connection 4 is preferably in the form of a magnetic gripper or a pneumatic gripper. The power supply to the head is provided by means of one of two electrical connections 5, comprising a transmitting part 5a located on the side of the robot arm 3 or 3a and a receiving part 5b located in the head 2, forming a transmitting-receiving system. This system may be a set of electrical contacts. Preferably, the transmitting-receiving system is a wireless electrical power transmission system, for example, an inductive system or a capacitive system. The head is equipped with a known printing unit 6 for continuous filament printing, comprising an extruding nozzle, a filament reservoir, and a polymer reservoir.

An exemplary composite element with a hybrid structure in the first embodiment of the invention 1 has a structural core 1a with a heterogeneous structure, defined at the design stage of the composite element. This structure is shown in Fig. 3 as a frame constituting a spatial arrangement, which is covered with an outer layer 1b. The heterogeneous structure of the core manifests itself in the fact that the structure has the character of a spatial network, the weave, segment lengths, and material density of which vary in different parts of the core so as to obtain the desired local mechanical parameters, i.e., stiffness, vibration damping, etc. The outer layer 1b is a composite containing fibers bonded by a polymer matrix, which are arranged in a directional manner in this layer. The fiber orientation imparts special characteristics to the outer layer, significantly improving the quality of composite element 1. The hybrid structure of composite element 1, comprising a heterogeneous core structure 1a and an outer layer 1b with oriented fibers, constitutes a three-dimensional component with a predetermined shape manufactured using two different 3D printing technologies. The mechanical and strength properties of this component are significantly improved compared to uniform components manufactured using 3D printing technology. The outer layer 1b, with oriented fibers bonded by a polymer matrix, is manufactured using continuous fiber 3D printing technology. The structural core 1a is made of a material adapted to form a permanent bond with the polymer matrix of the outer layer 1b. The material from which the structural core 1a is made can be identical to the polymer matrix of the outer layer 1b to achieve the best possible bond between the structural core and the outer layer. In this case, the recycling process for the element is significantly simplified. The outer layer 1b may comprise different types of fibers with different mechanical parameters, and the fibers may be selected from, for example, glass, carbon, aramid, flax, basalt or hemp fibers.

An exemplary composite element with a hybrid structure in the second embodiment of the invention 1' has a structural core 1'a with a heterogeneous structure, such as in the first embodiment of the invention. This structure is shown in Fig. 4 as a frame constituting a spatial arrangement, on the surface of which, in directions susceptible to deflection, fibers 1c made of electroshrinkable material of the artificial muscle type are incorporated, these fibers being controlled, for example, by means of electrical pulses, wherein neither the electrical connections of the fibers 1c nor their control system are shown in the drawing. The core 1'a together with the fibers 1c are covered with an outer layer 1b. The outer layer 1b is a composite containing fibers bonded with a polymer matrix, which are arranged in this layer in a directed manner, as in the first embodiment of the invention. The artificial muscle fibers 1c and their arrangement on the core 1'a are also defined at the design stage of the composite element with a hybrid structure 1' in such a way that the contraction and expansion of the fibers 1c influence the deflection of the composite element 1' in directions with a defined high elasticity.

Claims (17)

1. A method of manufacturing composite elements with a hybrid structure using a printing head using computer modeling for the manufactured composite elements and controlling the printing head according to algorithms previously prepared for printing elements in 3D technology, characterized in that in the first stage of the method, a structural core (1a) or (1'a) with a heterogeneous structure is printed in 3D printing technology in accordance with a model and algorithm previously adapted for making a heterogeneous core structure, and then in the second stage of the method, on the outer surface of the structural core (1a) or (1'a), the printing head (2) prints an outer layer (1b) with a continuous fiber in a polymer matrix in 3D technology, the fibers of which are arranged directionally in accordance with a model and algorithm previously adapted for controlling the movement of the printing head (2) to make the outer layer (1b). 2. A method according to claim 1, characterized in that additional fibers (1c) made of an electroshrinkable material of the artificial muscle type are incorporated into the surface of the structural core (1'a). 3. A method according to claim 1, characterized in that the inhomogeneous structure of the structural core (1a) or (1 'a) is modeled and printed according to an algorithm taking into account the local mechanical properties of the structural core (1a) or (1 'a), respectively, optimized with respect to the directional arrangement of the fibers in the outer layer (1b) and relating to the strength properties of the outer layer (1b). 4. A method according to claim 1, characterized in that the directional arrangement of the fibers in the outer layer (1b) is determined at the stage of modeling the composite element (1) or (1') taking into account the non-uniform mechanical properties of the composite core (1a) or (1'a), respectively. 5. The method according to claim 1, characterized in that the 3D printing of the structural core (1a) or (1'a) is performed using the powder method. 6. A method according to claim 1, characterized in that the movement of the printing head (2) is controlled by one robot arm (3) to which the head (2) is mechanically and electrically connected. 7. The method according to claim 1, characterized in that the control of the movement of the printing head (2) is performed by two arms (3) and (3a) of the robot, to which the head (2) is alternately connected mechanically and electrically. 8. A head for manufacturing composite elements with a hybrid structure, located on the arm (3) and/or (3a) of an industrial robot, which is intended for printing composite elements using 3D printing technology, which is equipped with a printing unit for continuous filament printing, characterized in that it has at least two mechanical head connections (4b) securing the head (2) to one of the robot arms (3) or (3a) and has at least two receiving elements (5b) of the energy transfer system (5), and each of the robot arms (3) or (3a) is equipped with a transmitting element (5a) of the energy transfer system and a mechanical arm connection (4a) compatible with each of the mechanical connections (4b) of the head (2), which after connection constitute a mounting element of the head (4). 9. The head according to claim 8, characterized in that the element (4) fastening the head (2) to the robot arm (3) or (3a) is a pneumatic gripper or a magnetic gripper. 10. The head according to claim 8, characterized in that the receiving element (5b) of the energy transmission system (5) and the transmitting element (5a) of the energy transmission system (5) are contact systems or wireless systems. 11. The head according to claim 8, characterized in that it comprises a printing unit (6) adapted to print only one type of fiber with specific mechanical properties, and for each other type of fiber a separate head or heads are used, which are used interchangeably. 12. A composite element with a hybrid structure, having the form of a three-dimensional component with a given shape (1, 1'), characterized in that it comprises a structural core (1a, 1'a), constituting a skeleton of the three-dimensional component, having the form of a non-uniform three-dimensional structure made using 3D printing technology, on which an outer layer (1b) with directed fibers, bound with a polymer matrix, is permanently located, said outer layer (1b) being made using 3D printing technology with continuous fibers. 13. A composite element according to claim 12, characterized in that the structural core (1'a) contains additional fibers made of an electroshrinkable material of the artificial muscle type, which are incorporated into the surface of the core (1'a). 14. A composite element according to claim 12, characterized in that the structural core (1a, 1'a) is made of a material adapted to form a permanent connection with the polymer matrix of the outer layer (1b). 15. A composite element according to claim 12, characterized in that the material from which the structural core (1a, 1'a) is made is identical to the polymer matrix of the outer layer (1b). 16. A composite element according to claim 12, characterized in that the outer layer (1b) contains different types of fibers with different mechanical parameters. PL 249474 Β1 17. A composite element according to claim 16, characterized in that the fibers of the outer layer (1 b) are at least two types selected from glass, carbon, aramid, flax, basalt or hemp fibers.